The antiproton is the antiparticle of the proton. Though stable, antiprotons are typically short-lived, because any collision with a proton will cause both particles to be annihilated in a burst of energy.
Predicted by Paul Dirac in his 1933 Nobel Prize lecture, the existence of the antiproton with −1 electric charge, opposite to the +1 electric charge of the proton. Dirac received the Nobel Prize for his previous 1928 publication of his Dirac equation that predicted the existence of positive and negative solutions to the Energy Equation ( E = m c 2) of Einstein and the existence of the positron, the antimatter analog to the electron, with positive charge and opposite spin.
In 1955, the antiproton was first experimentally confirmed at the Bevatron particle accelerator by University of California, Berkeley physicists Emilio Segrè and Owen Chamberlain. They were later awarded the 1959 Nobel Prize in Physics. An antiproton, in terms of valence quarks, is made up of two up antiquarks and one down antiquark (uud). The properties of the antiproton that have been measured all match the corresponding properties of the proton, with the exception that the antiproton has electric charge and magnetic moment that are the opposites of those in the proton.